The geology of the Preesall Saltfield area:

This report was commissioned by Canatxx Gas Storage Limited, who requested BGS produce an assessment of the geology of the Preesall area and a 3D model of the (Triassic) Preesall Halite. The work was required ahead of a Public Inquiry into the proposed development of an underground gas storage facility in an area to the east of the River Wyre and west of a former ICI brinefield. The main brief was to assess the geology, review borehole data held by BGS and additional borehole and seismic reflection data made available to BGS by Canatxx, and thereby provide the best-fit model from the current database. This has been completed. This report therefore considers the data both held by BGS and supplied to BGS by Canatxx and/or Mott MacDonald, for the purposes of this study. The British Geological Survey (BGS) already possess a considerable borehole database. BGS was also supplied with the Canatxx database of the tabulated top and base salt of those ICI brinefield wells and shaft data that were not already available to, or held by, BGS. The result is that 745 boreholes over the western Fylde area that were pertinent to the study were coded and entered in to the model. Several seismic reflection lines were also made available and have been reprocessed as part of this study. At a late stage, BGS gained access to velocity (sonic log) information from the Arm Hill and The Heads boreholes. These boreholes were drilled in early 2004 and permit calibration of the seismic reflection data, and identification of the Preesall Halite interval within the seismic data. The findings and conclusions reached here will contribute to the other proofs of evidence to be submitted on behalf of Canatxx Gas Storage Limited for the Public Inquiry. It should be noted that this report forms a wholly independent assessment of the location, extent, and general characteristics of the Preesall Saltfield. The report has not considered points of issue such as rock salt (halite) quality and its suitability for underground gas storage as this is to be covered by other consultants’ expert in these fields